A METHOD FOR BETTER ESTIMATING BLOOD PRESSURE IN HYPERTENSIVE PATIENTS

Background- An elevated arterial pressure is probably the most important public ‎health problem in developed countries. Although the measurement of blood pressure ‎in the clinic has been the cornerstone of the diagnosis and management of ‎hypertension, it has some limitations. Ambulatory blood pressure monitoring (ABPM) ‎is a method of blood pressure assessment which compensates for some of the ‎limitations and errors of clinical values such as the white coat phenomenon.‏ Methods- In this cross sectional study, we enrolled 42 (20 male, 22 female) ‎hypertensive patients who were under treatment. Each patient s BP was measured in ‎clinic twice at 5minute intervals. ABPM having been set up, each patient s blood ‎pressure was measured at 30- minute intervals during the day and 60- minute intervals during the night. The ‎patients were advised to do regular daytime activities and record unusual activities. ‎Results- The mean clinic BP 137.95±14.28/88.66±9.53 (mmHg) compared with a ‎mean awake ambulatory BP (ABP) of 132.90±12.27/80.51±7.39 (mmHg). A white ‎coat effect (Clinic-Ambulatory BP > 20/15mmHg) was present in 33.3% (19.15%-‎‎47.55%, CI 95%) of the individuals. The correlation coefficient of systolic pressure, ‎diastolic pressure and heart rate between clinic and awake ambulatory measurements ‎was 0.55, 0.48 and 0.57, which indicated a linear relationship (P<0.001). Multiple ‎regression models showed that age, gender, occupation and the duration of ‎hypertension (by year) after diagnosis have no significant effects on estimating awake ‎ABP by clinical measurements but could lead to a better estimation‏.‏
Conclusion- The frequent occurrence of white coat phenomenon in these patients ‎suggests that clinic BP assessment may not always represent usual awake ambulatory ‎BP in patients receiving antihypertensive therapy. We also suggest that physicians ‎who do not have the availability of ABPM use this model to estimate average awake ‎BP by clinic BP measurements: awake systolic BP (mmHg)=0.52 x clinic systolic BP ‎‎+ 66; awake diastolic BP (mmHg) = 0.46 x clinic diastolic BP + 42; and awake heart ‎rate (p/min) _ 0.33 x clinic heart rate + 52(Iranian Heart Journal 2003; 4 (4):25-30‎‏).